The present invention relates to amplifiers and more particularly to a wide band amplifier using bipolar transistors.
For an amplifier intended for amplifying a wide bandwidth signal such as a video signal, it is necessary to minimize the amplifier's distortion. For this purpose, a technique for suppressing distortion by employing negative fedback has been extensively used. However, negative feedback cannot be employed without decreasing the amplification factor. Accordingly, in order to obtain a desired amplification factor, it is necessary to use a number of amplifying elements or amplifier circuits. In this case, the stability of the entire amplifier circuit is lowered, which may result in oscillation.
The input and output characteristic between the base and emitter of a transistor used as an amplifying element is non-linear. In order to overcome the non-linearity, a technique wherein a large current is used and a technique in which negative feedback is employed have been used. However, none of these have been found to be totally acceptable. Especially, the negative feedback technique still involves the above-described difficulties.
Accordingly, an object of this invention is to provide a transistor amplifier in which the non-linear distortion of transistors is eliminated without employing negative feedback.